The overall role of the Viral Immunology Core is to provide a standard platform to characterize the properties of new Env genes generated by this HIVRAD program and to evaluate the epitope specificity and neutralization breadth and potency of sera and monoclonal antibodies generated by the other projects. This will include the following activities: 1) Preparation of standard stocks of HIV-1 and SHIV viral supernatants for neutralization assays. Single-round replication-competent HIV-1 pseudotyped viruses and functional SHIV genomes will be generated by transfecting HEK293 cells. The titers of these viruses will be determined and stocks will be stored for use by this Core and provided to other members of the Program as needed. 2) Performing neutralization assays with human and monkey mAbs and pAbs generated by this program. These antibodies will be tested against parental and modified HIV-1 and SHIVs produced by the Molecular Biology Core. Envs neutralization breadth will be determined against panels of 24 tier 2 subtype B and C pseudoviruses. 3) Mapping the antibody binding epitopes in the envelope proteins of infected monkey sera and monoclonal antibodies. This will be done by performing: a) ELISAs to peptides, fusion proteins and rgp120 proteins, b) neutralization assays with existing (over 200) and newly constructed chimeric or mutant HIV-1 pseudoviruses, c) FACS analysis of cells transfected with selected Envs, d) fractionation of human and monkey sera by affinity adsorption on protein columns. The data generated by this Core will be evaluated and provided to Dr. Pinter and other co-investigators in this program in graphical and tabular forms and analytical reports. These data will be presented on internal teleconferences, scientific meetings and submitted for publications. The experimental procedures to be performed in this core have been routinely used in this laboratory for a number of years, as confirmed by an established record of publications.